On Mon, 12 Apr 2010 17:32:47 -0500, "Dave" wrote:


"Hammy" wrote in message
.. .
On Mon, 12 Apr 2010 15:52:09 -0500, "Dave" wrote:




Okaaay. Thanks Fred. Just out of curiousity, what made you think of
this?
Is there some dark secret about the 555 that I have somehow missed?

Many thanks. Off to the workbench...

Dave


Hi Dave

Go here and read the part "Selecting External Components". You'll find
the answer to your ?

http://www.williamson-labs.com/555_apps.htm

Hey Hammy. Checked it out, but it didn't really tell me anything I didnt
already know. If the problem were simply the signal being out of expected
parameters, or the resistors/cap being high or low in value, I would still
have some kind of signal to work with. Instead pin 3, which is the output,
goes to ground as soon as the power is turned on. As I told Fred I think I
have to have something hooked up wrong. Just have to figure out what it
is...

---
Well, according to:

Version 4
SHEET 1 880 788
WIRE 224 192 -272 192
WIRE 544 192 448 192
WIRE -272 256 -272 192
WIRE -224 256 -272 256
WIRE -112 256 -144 256
WIRE 224 256 -112 256
WIRE 512 256 448 256
WIRE -112 320 -112 256
WIRE -80 320 -112 320
WIRE 48 320 0 320
WIRE 160 320 48 320
WIRE 224 320 160 320
WIRE 608 320 448 320
WIRE 480 384 448 384
WIRE 48 432 48 320
WIRE 608 480 608 320
WIRE 160 560 160 320
WIRE 512 560 512 256
WIRE 512 560 160 560
WIRE -272 592 -272 256
WIRE 480 592 480 384
WIRE 480 592 -272 592
WIRE -272 608 -272 592
WIRE -272 704 -272 688
WIRE 48 704 48 496
WIRE 48 704 -272 704
WIRE 544 704 544 192
WIRE 544 704 48 704
WIRE 608 704 608 560
WIRE 608 704 544 704
WIRE -272 768 -272 704
FLAG -272 768 0
SYMBOL Misc\\NE555 336 288 M0
SYMATTR InstName U1
SYMBOL voltage -272 592 M0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL res -96 304 M90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 58 VTop 0
SYMATTR InstName R1
SYMATTR Value 47
SYMBOL res -240 240 M90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 47
SYMBOL res 624 464 M0
WINDOW 0 -45 40 Left 0
WINDOW 3 -59 71 Left 0
SYMATTR InstName R3
SYMATTR Value 1000
SYMBOL cap 64 432 M0
WINDOW 0 -33 32 Left 0
WINDOW 3 -39 58 Left 0
SYMATTR InstName C1
SYMATTR Value 1e-6
TEXT -104 728 Right 0 !.tran .001 uic

it will oscillate, but that's for a bipolar 555, and at a frequency of
about 8.7 kHz.

If I had to guess, which I do, I'd guess that if pin 3 goes low when Vcc
goes high, and stays low, then you've either got the RESET pin wired to
GND or...


JF